JP3891328B2 - Data processing apparatus and data processing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a data processing device and a data processing method, and more particularly to a data processing device and a data processing method in image processing such as digital watermarking and falsification detection on an image.
[0002]
[Prior art]
Conventionally, a digital image data processing method is applied as, for example, a method for detecting falsification of an image obtained by a digital camera, a FAX, or the like and an information embedding processing method.
[0003]
Generally, there is an electronic signature as a means for verifying data tampering. In the electronic signature, signature information is created from data to be guaranteed, and the information is stored in a part of the image file or in another file. At the time of verification, signature information is created again from the image data, and the presence or absence of falsification is determined by comparing with the original signature information stored in the image file or another file.
[0004]
Japanese Patent Application Laid-Open No. 11-98344 is a prior art invention example 1 similar to the present invention in the technical field. In the first invention example 1, the original image and the watermark image corresponding to the original image are respectively registered in the management device, and the composite image suspected of unauthorized tampering is compared with the original image registered in the management device. Then, a watermark image is extracted from the difference, the extracted watermark image is compared with a watermark image registered in advance in the management apparatus, and if the result does not match, it is determined that the image has been tampered with.
[0005]
In Japanese Patent Application Laid-Open No. 10-208026 of Invention Example 2 of the prior application, embedding of a watermark image is used to determine whether or not tampering has occurred and to specify the tampering location.
[0006]
[Problems to be solved by the invention]
However, the conventional method using the electronic signature can be handled only in a specific file format because it is necessary to store the signature information in the file. In addition, it is a determination as to whether or not the original is the verification result, and this involves a problem that it is not possible to specify a falsification point.
[0007]
The method disclosed in Japanese Patent Application Laid-Open No. 11-98344 of Invention Example 1 of the prior application requires that an original image and a watermark image corresponding to the original image be registered in advance, which is a great practical limitation. It becomes.
[0008]
The method disclosed in Japanese Patent Application Laid-Open No. 10-208026 of Invention Example 2 of the prior application makes it possible to verify subsequent tampering by embedding watermark information. However, once a watermark is embedded, information beyond that is regarded as information embedding falsification, so information embedding can be performed only once.
[0009]
It is an object of the present invention to provide a data processing apparatus and a data processing method with improved tampering detection reliability.
[0010]
[Means for Solving the Problems]
In order to achieve such an object, the invention described in claim 1 is a data processing device that embeds falsification detection information for detecting falsification of an image. Among pixels constituting an image, a pixel that embeds falsification detection information, and falsification detection information. Pixel determination means for determining a pixel to embed additional information, which is information other than the above, a detection information embedding means for embedding the falsification detection information in a pixel for embedding the determined falsification detection information, and a pixel for embedding the determined additional information Additional information embedding means for embedding additional information, and the additional information embedding means embeds additional information by embedding additional information using a preset number of pixels for one additional information. and features that you can embedded.
[0011]
The invention described in claim 2 is the data processing apparatus according to claim 1, further comprising key information input means for inputting key information, wherein the pixel determining means is key information input by the key information input means. Based on the above, a pixel for embedding additional information is determined.
According to a third aspect of the present invention, in the data processing apparatus according to the first or second aspect, the detection information embedding unit and the additional information embedding unit embed the least significant bit of the pixel.
Furthermore, the invention described in claim 4 is the data processing apparatus according to claim 2, wherein the pixel determining means determines a pixel to embed additional information by a pseudorandom number obtained from the key information input by the key information input means. It is characterized by.
[0012]
According to a fifth aspect of the present invention, there is provided a data processing method for embedding tamper detection information for detecting tampering of an image. Among pixels constituting an image, addition of a pixel for embedding the tamper detection information and information other than the tamper detection information. A pixel determination step for determining a pixel to embed information, a detection information embedding step for embedding the falsification detection information in the pixel in which the determined falsification detection information is embedded, and additional information in which additional information is embedded in the pixel in which the determined additional information is embedded An additional information embedding step, wherein the additional information embedding step enables embedding of the additional information by embedding additional information using a preset number of pixels. And
[0013]
The invention according to claim 6 is the data processing method according to claim 5, further comprising a key input information step for inputting key information, wherein the pixel determining step is the key information input in the key information input step. Based on the above, a pixel for embedding additional information is determined.
According to a seventh aspect of the present invention, in the data processing method according to the fifth or sixth aspect, the detection information embedding step and the additional information embedding step embed the least significant bit of the pixel.
Further, the invention according to claim 8 is the data processing method according to claim 6, wherein the pixel determining step determines a pixel in which the additional information is embedded by a pseudo random number obtained from the key information input in the key information input step. It is characterized by.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of a data processing apparatus and a data processing method according to the present invention will be described in detail with reference to the accompanying drawings. 1 to 4 show an embodiment of a data processing apparatus and a data processing method of the present invention. FIG. 1 shows the overall configuration. FIG. 2 shows an example of the operation flow of the present invention.
[0015]
The present invention is a further improvement of the unpublished prior application invention of the inventor. In this prior invention, falsification detection data is embedded in each pixel. The detection data is embedded in the least significant bit of each pixel. The detection data is calculated from the pixel value of the pixel and a pseudo random number . The method of the previous application is a method for falsification verification. In contrast to this, the present invention makes it possible to embed information multiple times while preventing substantial tampering. By embedding detection data in each pixel, it is possible to determine whether or not tampering has occurred and to specify the tampering location.
[0016]
1, the image data processing apparatus to which the present invention is applied has a key input unit 1, an encoding unit 2, a decoding unit 3, a control unit 4, a data input unit 5, a pseudo random number generation unit 6, and a memory 7. Configured.
[0017]
The encoding operation of the embodiment will be described with reference to the flowchart of FIG. First, target image data is input (step 201). Next, key information is input (step 202). A random number is initialized with the input key information (step 203). Further, the information embedding position is specified based on the input key information (or a pseudo random number generated thereby) (step 204).
[0018]
FIG. 3 shows an example of the information embedding position. The information embedding position is generated from the key information. For example, pseudo-random numbers are generated from key information and embedded every numerical interval (5, 12, 18, 4, 10,...) (Pixels are numbered one-dimensionally by raster scanning from the upper left. To do). If the pixels are too close, the number of tampering verification pixels is reduced. Therefore, the random number value is selected with a threshold value, and a small value (for example, 9 or less) is not used (in the above example, 12, 18 , 10,...
[0019]
The embedded information has a predetermined size. For example, if the embedded information is 4 bits, 1 bit is attached to the embedded information, and 5 bits are used as one unit. Then, “1” is set when the information is embedded, and “0” is set when the information is not embedded.
[0020]
For example, it is assumed that the information embedding pixel is “18” in the entire image. The embedding pixels are grouped every 5 pixels in order from the top. If it is 18 pixels, it becomes “5, 5, 5, 3”, and the last 3 pixels are not used. For the first information embedding, the first five pixels are used, and the first one pixel is a flag indicating the presence or absence of embedding, so the least significant bit is “1” (the information embedding uses the least significant bit of each pixel. ). For the next five pixels, at least the first pixel has a flag of “0”, and the remaining four pixels are arbitrary (the original image may be left as it is).
[0021]
When the information is embedded for the second time or later, the steps shown in the flowchart of FIG. 2 are performed from the beginning, and it is confirmed whether or not the information has already been embedded last time when specifying the embedded position. An embedding unit with a flag of “1” (in this case, 5 pixels) is skipped, and information is embedded in the first embedding unit with a flag of “0”. For example, in the example of the previous 18 pixels, when the first unit (5 pixels) has been embedded, the next unit is used. If the next unit has already been embedded, use the next unit. If all the units have been embedded, it is assumed that no more information can be embedded, and a warning is displayed to the user.
[0022]
Since information embedding is performed in step 206, at this point (step 204), the following is performed.
・ Identification of all embedding pixels.
The process is performed until the first embedding unit (in this case, 5 pixels) that is empty (the flag is “0”) is specified.
[0023]
Once the information embedding position has been specified, the process for each pixel is performed (step 205 and subsequent steps). First, it is determined whether or not the pixel is an information embedding position (step 205). It is determined whether it is the current embedding position obtained in step 204. If it corresponds to the embedding position, information embedding processing is performed (step 206). Information embedding uses the least significant bit of the target pixel. The data to be embedded (1 bit) is used as the least significant bit as it is.
[0024]
In this example, the flag is 1 bit and the information is 4 bits. Therefore, in order to use 5 pixels, it is necessary to calculate in step 205 not only whether the pixel of interest is an “information embedding pixel” but also what number it corresponds to among the 5 pixels.
[0025]
For example, if the target pixel is the first, the flag information is embedded, and if it is the fourth, the third bit of the embedded information is embedded. If it is determined in step 205 that the position is not the information embedding position, falsification verification data is generated and embedded (steps 207 to 209). When all the pixels have been processed, the encoding is finished (step 210). This is the end of the description of the operation flow during encoding.
[0026]
Next, the operation flow during decoding will be described with reference to FIG. First, target image data is input (step 401). Next, key information is input (step 402). A random number is initialized with the input key information (step 403). Also, the information embedding position is specified by the input key information (or a pseudo random number generated thereby) (step 404). The position is specified in the same way as encoding.
[0027]
Next, processing is performed for each pixel. First, it is determined whether it corresponds to the information embedding position (step 405). If this is the case, embedded information is extracted (step 406). The embedded information is embedded in the least significant bit of each pixel in units of 5 pixels at the time of encoding, and there are also pixels that are vacant for additional writing (information is not embedded). If the least significant bit of the first pixel is ON in units of 5 pixels, the bits extracted from the remaining 4 pixels are stored as embedded information. When the flag bit is OFF, information is not extracted or is not stored even if it is extracted. If it is not the information embedding position, tampering verification is performed (steps 407 to 410). This is the end of the description of the decoding process.
[0028]
In the above embodiment, the embedding information is 4 bits. However, if the number of pixels of the entire image is large, it can be easily increased. The embedded information can be encrypted using a key or the like. In addition, the falsification position detected in step 410 can be displayed superimposed on the image, and the falsification position can be presented to the user in an easily understandable manner. If tampering is detected in step 410, the embedded information is invalid because it may be tampered with. Alternatively, it is possible to present to the user that there is a possibility of falsification.
[0029]
【The invention's effect】
As is clear from the above description, the data processing apparatus and data processing method of the present invention embed any information in the digital image data invisible in the digital image data and data for verifying tampering. According to this processing, information can be embedded at the same time as falsification verification, and the information embedding position is unknown without a key, and it is difficult to rewrite intentionally.
[0030]
In addition, since the remaining pixels are verified for alteration, if the image is changed without specifying the information embedding position, even if the embedded information changes accidentally, the change of the remaining pixels is found by the alteration verification. Can be invalidated. Furthermore, adding information is strictly a kind of alteration because the image changes, but it is a change that does not substantially change the image content, so it is a significant change in appearance from the first original image Can guarantee that there is no.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration example of an image data processing apparatus to which an embodiment of a digital image data processing method of the present invention is applied.
FIG. 2 is a flowchart showing an encoding operation of the embodiment.
FIG. 3 is a diagram illustrating an example of an information embedding position.
FIG. 4 is a flowchart illustrating an operation during decoding according to the embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Key input part 2 Encoding part 3 Decoding part 4 Control part 5 Data input part 6 Pseudorandom number generation part 7 Memory

Claims (8)

In a data processing apparatus that embeds falsification detection information for detecting falsification of an image,
Among the pixels constituting the image, a pixel determining unit that determines a pixel in which the alteration detection information is embedded, and a pixel in which additional information that is information other than the alteration detection information is embedded.
A detection information embedding unit that embeds the falsification detection information in a pixel in which the determined falsification detection information is embedded;
An additional information embedding unit that embeds the additional information in a pixel in which the determined additional information is embedded;
Have
The additional information embedding unit can embed a plurality of additional information by embedding the additional information using a preset number of pixels for the one additional information. apparatus. Furthermore, it has key information input means for inputting key information,
The data processing apparatus according to claim 1, wherein the pixel determining unit determines a pixel in which the additional information is embedded based on the key information input by the key information input unit. The data processing apparatus according to claim 1, wherein the detection information embedding unit and the additional information embedding unit embed the least significant bit of the pixel. The data processing apparatus according to claim 2, wherein the pixel determining unit determines a pixel in which the additional information is embedded based on a pseudorandom number obtained from the key information input by the key information input unit. In a data processing method for embedding tamper detection information for detecting tampering of an image,
Among the pixels constituting the image, a pixel determination step for determining a pixel for embedding the alteration detection information and a pixel for embedding additional information that is information other than the alteration detection information;
A detection information embedding step of embedding the falsification detection information into a pixel in which the determined falsification detection information is embedded;
An additional information embedding step of embedding the additional information in a pixel in which the determined additional information is embedded;
With
In the additional information embedding step, a plurality of additional information can be embedded by embedding the additional information by using a preset number of pixels for one additional information. Method. Furthermore, it has a key input information step for inputting key information,
6. The data processing method according to claim 5, wherein the pixel determining step determines a pixel in which the additional information is embedded based on the key information input in the key information input step. 7. The data processing method according to claim 5, wherein the detection information embedding step and the additional information embedding step perform embedding in the least significant bit of the pixel. The data processing method according to claim 6, wherein the pixel determining step determines a pixel in which the additional information is embedded based on a pseudorandom number obtained from the key information input in the key information input step.

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